Flotation reagents and method of use



Patented Aug. 2, 1938 UNITED STATES FLOTATION REAGENTS AND LIETHOD OFUSE Antoine M. Gaudin, Butte, Mont.

No Drawing. Application December 24, 1929,

' Serial No. 416,291

5 Claims.

This invention relates to the recovery of values from ores by subjectingthe same to a flotation operation in the presence of certain reagents.

I have discovered that certain organic substances of the general formulaRSH (in which R denotes a hydro-carbon radical, S-sulphur, andI-Ihydrogen), such as mercaptans and thiophenols, are particularly goodcollectors of copper minerals, oxidized aswell as sulphides, as

- well as of the sulphides of zinc. Likewise the oxidation products ofthese organic hydro-sulphides such as the sulphides and di-sulphides aresubstantially as good collectors as the mercaptans themselves for thesulphide minerals only.

The use of these reagents in the recovery of minerals by flotation is ofparticular advantage in that they are not good collectors for ironsulphides such as pyrite or'pyrrhotite, and hence their use on pyriticcopper ores is particularly valuable in that they collect the copperminerals to the more complete exclusion of the iron minerals than isobtained through the use of other collectors, of which the xanthates aretypical.

The ability of mercaptans to collect oxidized copper minerals makes therecovery of the oxidized content of sulphide ores more eificient sincefrom to of the total copper loss in sulphide copper ores by flotation isdue to their oxidized content.

The mercaptans require less alkaline circuits than the xanthates for thesecuring of conditions which result in the depression of iron mineralsand therefore the use of the former in place of xanthates effectseconomiesin the use-of lime or corresponding alkali.

The higher alkyl mercaptans, that is, those in the series higher thanethyl mercaptan, to wit, propyl, butyl, amyl, hexyl, heptyl, octyl, areof particular advantage because of their greater collecting ability andtheir lesser volatility as compared to the mercaptans lower in series.The lesser volatility is of prime importance from a practical standpointbecause it lessens the discomfort caused by the semi-poisonous vaporsand loss of reagent.

I have discovered that the oxidation products of the mercaptans, thatis, the sulphides and disulphides, are substantially as good collectorsfor the sulphide ores as the mercaptans themselves. On the other hand,unlike mercaptans they do not react with dissolved base metal salts sothat they can be used with circuits containing various amounts of thesesalts without loss. In the case of certain ores the use of sulphides anddi-sulphides makes possible a considerable saving in the alkalinereagents which otherwise are required to eliminate the soluble saltsbefore using mercaptans or other flotation reagents, such as thexanthates.

As an illustration of the depressing effect of mercaptans upon ironminerals as compared with the xanthates, a flotation operation conductedin a circuit containing pure pyrite in the presence of 0.05 lb.- per tonof potassium ethyl xanthate, recovered the entire amount of the iron.Using the same amount of thio-beta-naphthol a concentrate was obtainedwhich contained 97% of the iron. When pure chalcolcite was subjected toa flotation operation under the same circumstances with the above, tworeagents the recovery was 62% and 96% respectively. In the same mannerthe recoveries of these minerals with 0.03 lb. per ton of potassiumethyl xanthate and isoamyl mercaptan, is respectively 93% and 86% forthe pyrite and 57% and 92% for the chalcolcite.

Similarly, in synthetic mixtures of pyrite and chalcolcite, xanthatefavors the recovery of pyrite, while mercaptans favor the recovery ofthe copper mineral. Upon mixtures consisting of 25 grams of minus 200and plus 400 mesh pure py-' rite, and 25 grams of the same size purechalcolcite, the following recoveries were obtained with amyl xanthateand amyl mercaptan, each used in the amount of .03 lb. per ton.

Chalcolcite recovery Pyrite re- Reagent covery Percent Percent Amy]xanthate Amyl mercaptan- Lb. per Iron re- Copper Reabent ton coveryrecovery Percent Percent Ethyl xanthate 0.05 72 81 Amy] xanthatm. 0. 0591 92 Amy] mercaptan 0. 05 74 93 In all of the above quoted tests afrother was. used in conjunction with the various collectors,

the amount of frother being the same in each case.

I have also found that the mercaptans are particularly well suited tocollect oxidized copper minerals such as malachite, azurite, cuprite andmelaconite. Thus an 80% recovery of malachite from a 10:40 mixtureofmalachite and calcite required 1.3 lbs. per ton isoamyl mercaptan or1.9 lbs. per ton n-butyl mercaptan, Whereas 2.0

lbs. per ton isoamyl xanthate and 4.1 lbs. per ton n-butyl xanthate wererequired to give the same recovery. Similar results were obtained withazurite.

A particularly good flotation of oxidized copper minerals by mercaptansis of interest in the flotation of sulphide ores since the. greaterportion of the copper loss in such minerals is due to the presence ofthe values in oxidized form. A sulphide copper ore carrying chalcopyriteas the principal copper mineral, assaying 1.95% copper, of which 0.17%was oxidized copper, gave a tailing of 0.26% copper when floated with0.10 lb. per ton sodium ethyl xanthate. The copper content of thetailing was reduced to 0.12% when isoamyl mercaptan was substitutedpound for pound for xanthate.

The following data illustrates the advantage secured from the use ofhigher mercaptans,

showing the amount of reagent in pounds per ton required to float 80% ofthe ore indicated.

In the above experiments the mercaptans or thioalcohols were added tothe flotation cell as alcoholic solutions. Obviously the reagent may beadded to the ball mill prior to flotation or to the flotation cell or tosome conditioning or emulsifying tank between the grinding and flotationstages. Reagent additions may be made in the solid or liquid form or' insolutions in some inert solvent such as methyl alcohol, an amine, aphenolic compound or one of the usual flotation oils, such as pine oils.The greater solubility of mercaptans as compared with .thiophenols is ofdistinct advantage in this particular.

The use of the higher hydrosulphides is advantageous as compared withthe use of the lower hydrosulphides in that the. former are considerablyless volatile than the latter and this, together with the fact thatsmaller amounts of the higher hydrosulphides are required, minimizes thedanger of the reagent occurring in the air to a dangerous concentration.

Further, I have discovered that the oxidation products ofv organichydrosulphides, especially sulphides and disulphides, are substantiallyas good collectors for sulphide minerals as are the hydrosulphidesthemselves. Copper-bearing sulphide minerals in particular are readilyfloated by organic'sulphides and disulphides.

Unlike organic hydrosulphides, organic sulphides do not react withdissolved base-metal salts. Flotation of sulphide ores containingsoluble salts is therefore prohibited if organic hydrosulphides are usedas reagents unless the pulp is first freed of the soluble salts by theaddition of a precipitation agent or other metal ion abstracting agent.-The use of sulphides or disulphides of the above type obviatesthenecessity and cost of adding such a precipitation agent.

The following table illustrates a flotation operation conducted upon thecopper-bearing sulphide mineral, chalcocite.

J de .05 amyl disulphide+0.25#/T hydrated OuSOl Similarly with a' copperore in which'the copper existed as chalcopyrite and chalcocite, togetherwith some copper in solution, the following results were obtained.

Amount of Recovery Reagent reagent percent- Benzyl mercaptan; 0. 10 40Benzyl mercaptan 0. l +Lime 4. 0 84 Benzyl disulphide 0. 87

I have furtherdiscovered that mercaptans or thiophenols are much moreeflicient as flotation reagents for sulphide zinc-bearing ores thanxanthates.

It has been known for some time that the use of soluble copper saltsmakes zinc sulphides more amenable to flotation reagents. I have foundthat the beneficial effects of copper salts in the flotation of zincsulphide is due to the formation of a thin coating of copper sulphideupon the surface of the mineral and furthermore that the copperactivated sphalerite is particularly amenable to flotation by reagentswhich are well suited to the flotation of cupriferous ores. Among thesereagents are the organic hydrosulphides and their oxidation products asabove set forth.

I have found that the use of mercaptans or thiophenols in floatingcopper activated sphalerite makes possible the floatability thereof overa substantially-extending alkaline range, which is not secured by theuse of xanthates Thus, with a certain amount of xanthate, materialdepression results at pH 12, whereas such an efiect doesrnot manifestitself when using the same amount ofthe corresponding mercaptan untilabout pH 13. This discovery is 'of practical value in the treating ofiron-bearing zinc ores or pyritic copper ores. It is illustrated in thefollowing table:

Recoveries. percent Reagents Zn Fe .75#/T CuSO 11,0 .10 K. ethylxanthate CaO .m r 011804, 5 mo .08 amyl mercaptan- 4.0 0:10

amyl hexyl and heptyl mercaptans as well as their oxidation products,are particularly efllcient for the purpose set forth. Broadly speaking,the reactions of these various compounds are similar and hence they areto be construed in this application as being typical and I do not wishto be I limited specifically to any of the particular reagents named,but the claims appended hereto should be construed broadly.

What I claim is:

1. A method of recovering values from oxidized ores which consists insubjecting the same to a flotation operation in the presence of an alkylmercaptan higher in the series than ethyl mercaptan.

2. A method of recovering values from oxidized copper and zinc oreswhich consists in subjecting the same to a-fiotation operation in thepresence of an alkyl mercaptan higher in the series than ethylmercaptan.

3. A method of recovering oxidized copper ore values from the gangues incrude copper ore, which consists in subjecting the crude ore' to a frothflotation operation in the presence of amyl mercaptan.

4. A method of recovering values from ores containing both sulfides andoxidized products of the same metal which comprises subjecting the sameto a flotation operation in the presence of an alkyl mercaptan higher inthe series than ethyl inercaptan.

5. A method according to claim 4 in which the ore contains coppersulfide and oxidized copper compounds.

ANTOINE M. GAUDIN.

